[Request] A dehumidifier for a very humid guest bedroom

I live in a humid area and have a guest bedroom that I need to dehumidify. I estimate the room is around 200 sq ft and the humidity in there is constantly going into the high 60s and 70s at night. The room is properly sealed and air conditioned, but it's located in a corner of the house and the humidity seems to collect there.

I bought a Ninesky CT2 and despite its claims and good reviews, I find that it just isn't anywhere near strong enough. It's not capable of pulling enough water from the air to keep up with demand. Even with the door closed, It's making absolutely no difference at all.

I'm looking for a good dehumidifier that can keep the room around 40-50% humidity. Thank you!